Mechanical and thermal properties of Mo for packaging HgCdTe IRFPA detector at cryogenic temperatures

Abstract

Listen

Translate article

Molybdenum (Mo), as an electronic packaging material with excellent comprehensive performance, is widely used in the lead substrate and cold platform of HgCdTe infrared focal plane detector assembly. The thermodynamic parameters of molybdenum in the temperature ranging from 300 K down to 4.2 K are obtained by the thermodynamic tests in this paper. Mechanical properties and microstructure of Mo at 300 K, 77 K and 4.2 K are analyzed with the use of tensile tester and scanning electron microscope. Results show that: the average linear expansion coefficient of molybdenum between 300 K and 4.2 K is 3.21 × 10-6 /K, and molybdenum has the properties of high thermal conductivity and low specific heat capacity at cryogenic temperature. The elastic modulus of molybdenum increases, and the tensile strength and elongation decrease with decreasing temperature in the temperature ranging from 300 K down to 4.2 K. According to the macroscopic and microscopic morphology of tensile fracture, the fracture mode at 300 K is the ductile–brittle mixed fracture mode, and the material turns from ductile at 300 K to brittle at 77 K and 4.2 K. The fracture behaviors are transgranular fracture at 77 K and intergranular fracture at 4.2 K, respectively.